Liquid crystal display devices are flat display devices which have excellent features such as high definition, low profile, light weight, and low power consumption. In recent years, a market scale of liquid crystal display devices has been rapidly increasing due to improved display performance, increased production capacity, and improved price competitiveness against other display devices.
In a twisted nematic mode (TN mode) liquid crystal display device which is widely used today, long axes of liquid crystal molecules having positive dielectric anisotropy are aligned substantially parallel to a substrate surface, and the long axes of the liquid crystal molecules are twisted by substantially 90° between upper and lower substrates along a thickness direction of a liquid crystal layer. When a voltage is applied to the liquid crystal layer, the liquid crystal molecules are aligned parallel to an electric field, and twist alignment is eliminated. In a TN mode liquid crystal display device, light transmittance is controlled by utilizing a change in optical rotation caused by a change in alignment of liquid crystal molecules which occurs due to voltage application.
In designing a panel of such a liquid crystal display device, it is necessary that retardation of light be a desired value in order to realize as high transmittance as possible.
Here, a retardation value u is determined by the following equation:u=2Δnd/λ
where Δn is refractive index anisotropy (birefringence) of a liquid crystal material, d is a cell thickness, and λ is a wavelength of light. According to the equation, the thickness (also referred to as cell thickness) of a liquid crystal layer of a liquid crystal display panel is determined based on the refractive index anisotropy Δn which is determined based on the type of the liquid crystal material, the wavelength λ of light used as a standard, and the retardation value u for obtaining the desired transmittance.
Generally, in a TN mode liquid crystal display device which displays a color image of mixed colors of R, G, and B, a cell thickness of a liquid crystal panel is determined on the basis of retardation which is based on the wavelength of blue light, which has the shortest wavelength among the three colors (red (R), green (G), and blue (B)) of color filters (see Patent Literature 1, for example).